Cops charged the hotheaded teenage boyfriend of a Bronx mom with beating her 4-year-old son to death – and charged her for sitting by idly – as horrific new details emerged yesterday of the savage days-long brutality inflicted on the little boy.

José Calderon, 18, was charged with second-degree murder in the senseless beating of Quachaun Browne, who was found dead Monday from a fractured skull and other severe internal injuries, police said.

The battered boy’s mother, Aleshia Smith, 26, was charged with second-degree manslaughter for not helping her son, police said. The couple was held pending arraignment late last night.

The abuse began last Thursday when a television crashed in the couple’s vermin-infested Bronx apartment. Calderon blamed it on the boy and began punching him and slamming him into the apartment’s walls, police sources said. This continued over the course of the next two days, the sources said.

On Saturday, the family went to a Chuck E. Cheese restaurant, where Quachaun began to vomit blood. The family returned home and Calderon beat the child again, the sources said.

By Sunday, the boy appeared severely ill, police said in citing admissions from the mother, and interviews with two older siblings who lived in the apartment.

It is believed the boy died sometime late that night. Early Monday, Smith told police she awoke to find Calderon trying to revive the child.

She told investigators she urged her boyfriend to let her call 911, but he said no, because he would get in trouble. At some point she managed to call police on a cellphone and paramedics arrived around 3:30 a.m., but the boy was already dead.

Calderon initially insisted to police that the boy’s injuries came when a television fell on top of him, but later told investigators he lost his temper and hit the child, police sources said.

Police said there was evidence that Quachaun had injuries from earlier beatings and that the four other children living in the family’s squalid Norwood apartment may have been beaten as well.

Quachaun Browne’s gruesome end came despite the months-long involvement of the Administration for Children’s Services with the family.

ACS caseworkers visited the family’s home six times since Nov. 15, an ACS source said.

The most recent visit was Jan. 12. Three additional visits were made to MS 280, the school the siblings attended. Quachaun and the four other children were interviewed, the source said. The case files also indicated Smith attended a “child safety conference” and had been receptive to agency efforts to help.

Caseworkers had no knowledge of Calderon, who neighbors said had moved in with Smith two months ago, the agency said.

ACS Commissioner John Mattingly said the overall case file should have prompted a “stronger response,” but insisted it does not suggest the agency “failed to act.”

erika.martinez@nypost.com

TIMELINE – CHRONOLOGY

JAN 26 – Thursday

A TV falls to the floor in the family’s home. Boyfriend José Calderon blames Quachaun Browne and begins punching him.